Wavelength division multiplexed (WDM) optical line systems (OLS) are designed to deliver relatively error free information traffic via, for example, a plurality of intermediate terminals or nodes connecting two end terminals or nodes. Each end terminal typically computes a bit error rate (BER) according to a protocol such as synchronous optical networking (SONET), SDH, gigabit-Ethernet and the like. If a fault occurs between the end nodes (as indicated by a high BER at the receiving end node), the location of the fault cannot be determined and, therefore, all intermediate nodes forming the communication link between the end nodes must be physically examined or tested to determine the location of the fault. Such a fault can be related to a failed hardware component or a fiber failure (fiber cut, cracked or bent fiber and the like).
The time to repair a fault in an optical line system is, therefore, related to the time needed to locate the fault, and this time increases greatly where the number of intermediate nodes is increased.